Thankfully it shows for PS3 as well as XBox 360, and won't be a one console game and both will be launching at the same time, apparently

Gamespot posted on their site:[UPDATE] At its pre-E3 press conference, Microsoft confirmed that the next Grand Theft Auto is coming to the Xbox 360 in October of next year. In an official announcement, Rockstar Games confirmed simultaneous launch on PS3. - Gamespot Article

Thanks to Damian and Miami13

Update

Microsoft have revealed at E3 that GTA IV will have downloadable add-ons from the XBox Live service. More details will follow as launch date nears.